Why gas consumption stats don’t add up

Originally published: March 19, 2012

Numbers sell cars. Sometimes, for the gearheads in the group, it’s the performance statistics: 0-100km/h, horsepower, lateral g-force, lap times around the Nürburgring. Sometimes it’s towing capacity or cubic meters of trunk space, seating capacity, pound-feet of torque, the length of the cargo bed.

Then there’s the all-important monthly payment, lease rates, 0.9% financing O.A.C., $29,900 plus Freight and PDI, yours for just $199 bi-weekly. The manufacturers bombard us with a constant stream of empirical data with why we should buy their product; why it’s the best car out there for YOU.

These days, there’s another number in the back of everybody’s minds, although we’ll all groan aloud when we see it: 1.50/ L for gasoline. The constantly increasing price of fuel means that customers walking into a showroom these days aren’t quite so interested in horsepower and torque. They want to know what the fuel-economy figures are, which is why they’re usually the biggest numbers on the window-sticker, second only to the total price. There’s just one problem.

In Canada, those fuel-economy figures are complete and utter nonsense.

Each year, Natural Resources Canada publishes their fuel consumption guide, and each year I idly flick through it to see the highlights and lowlights. The TDI Jetta, 4.7L/100km on the highway; not bad. The Lamborghini Aventador, 21.0L/100km in the city; oh, Lambo, LOL.

These are figures supplied to the NRC by the manufacturers themselves which, depending on your preference of barnyard metaphors, is either putting the cat among the pigeons or leaving the fox in charge of the henhouse. But that’s not really the problem.

The problem is in how the fuel-economy figures are determined, along with how the operating cost averages are then calculated. These are tests performed in the laboratory, and they are so far removed from reality that they could run for Provincial government.

This is what Natural Resource Canada thinks your city commute looks like. You hop in your car, fire it up from a "cold" start (summer temperatures), and drive twelve kilometres into work at an average speed of 32 km/h, with a short top speed burst of 91 km/h where, presumably, you had your usual brief morning street-race with Vin Diesel. You have 18 stops in total, and spend an average of four minutes idling the car. Then, when you arrive, you turn off the car, then turn it back on again and drive around the parking lot for 8 more minutes.

Oh, I forgot to mention: because these tests are performed in a laboratory setting, on a two-wheel dyno, you have just commuted to work in a total vacuum without any wind resistance. That probably explains why Mr. Diesel beat you this time despite the giant spoiler on his Toyota Corolla.

The highway test is even worse, although correction factors are applied to adjust for wind-resistance at highway speeds. This trip is 16 kilometres long and does not include any stops-clearly, not meant to simulate trying to get home on a Friday evening. The average speed is 77 km/h, with a top speed of 97 km/h. And I quote, "the speed varies to simulate different kinds of highway and rural roads."

As any hypermiler will tell you, the faster you go, the worse your fuel-economy gets. I’m not sure if you’ve driven anywhere on the Trans-Canada recently, but the average speed of the flow of traffic on the Number One is considerably higher than 77 km/h. In fact, set your cruise control at 97 km/h and sit in the fast lane and you will be surprised at how many little old ladies come up beside you, lean on the horn and flip you the bird with both fingers.

One final insult. Assuming that you were able to replicate the fuel economy figures suggested on the label of your brand new car (which probably won’t be performing its best until after the first oil change), Natural Resources Canada has provided you with a handy-dandy estimated yearly cost of driving your car. They even have a formula and everything.

It’s derived by taking an annual driving distance of 20,000 km per year, and assuming 55 per cent city driving and 45 per cent highway driving. Seems fair, I suppose, though everyone’s driving cycle will be a little different. The really stupid part comes when they take that total number of litres of fuel consumed annually and multiply it by the cost of fuel.

This is right out of my 2012 Guide: "Estimated fuel costs for 2012 are based on forecast prices of 1.05/L for regular gasoline, $1.15/L for premium gasoline, [and] $1.15/L for diesel fuel." Um, beg pardon?

Forecast? Forecast by whom? Somebody who rides to work on a tricycle powered by Unicorn smiles and happy thoughts? Are we expecting somebody to build a refinery on the site of the Olympic Torch or strike oil in Stanley Park? Maybe, just maybe you can pay fuel prices like that if you search carefully in Alberta, but the average cost of fuel is much higher than that, and completely out of whack for West Coasters.

So what’s to be done? Natural Resources Canada has a sort-of "dog ate my homework" clause in their guide, to whit, "It would be difficult to drive every model of new vehicle on the road… almost impossible to consistently duplicate on-road testing results because so many variables have an impact on the vehicle." Subtext: so we couldn’t be bothered.

On the other hand, the EPA instituted much more accurate procedures in the US in 2008, with brisker acceleration, the use of A/C and other power-sapping auxiliary systems and colder temperatures than the ideal summertime temps we use. So things can be improved.

As a consumer, there are three things you can do. First, remember that published Canadian fuel-economy figures are only estimates, but they are standardized, so can be useful to compare two different vehicles.

Secondly, assuming that the car or truck you’re looking at is also available in the U.S., try converting their numbers to get a slightly more realistic idea of how much your new vehicle is going to cost you. Remember that the U.S. gallon is smaller than the Imperial gallon: to get a figure in L/100kms, there are any number of conversion calculators available by doing a quick internet search.

Thirdly, keep in mind that the figures quoted are optimistic estimates and don’t be surprised when you don’t quite hit them. Keep your tires inflated and rotated, change your oil regularly, drive in a smooth, controlled manner without fast starts, and maybe even risk the wrath of those little old ladies with slightly slower speeds.